1. Field of the Invention
This invention relates to a magnetic record/reproduce head assembly, and in particular to a head assembly having a bi-directional read while write capability.
2. Description Relative to the Prior Art
In a magnetic tape recorder, a read while write capability is an essential feature for providing error free magnetically stored data. A read while write head assembly comprises a record head in-line with a contiguous read head; the gap of the read head being closely spaced to the gap of the record head, with the read head positioned downstream of the record head in the direction of tape motion. By continually reading "just recorded" data while writing, the quality of the recorded data is immediately determinable at a time while the original data is still available in temporary storage in the recording system. The reproduced data is checked against the original data, and appropriate action, such as re-recording, taken in case of error.
Many modern tape systems require operation where writing and reading of the data occurs for either direction of tape travel. The streaming tape system where the recording is laid down on the tape in a serpentine pattern for alternate directions of tape travel is an example of such a bi-directional recording system. Incorporation of read while writing capability for bi-directional operation necessitates a head assembly consisting of a first write head adjacent to a read head which is adjacent to a second write head, or a first read head adjacent to a write head which is adjacent to a second read head. The choice between these head assembly configurations depends upon specific overall system design considerations.
Concurrent with bi-directional operation, the present trend in magnetic recording calls for higher data transfer rates and higher data packing density on the tape. Higher packing density is synonymous with shorter recorded wavelength and, as is known in the art, signal spacing loss during both record and reproduce operations becomes increasingly severe with decreasing recorded wavelength. Intimate contact between the tape and the head is therefore required to preclude signal deterioration due to the spacing loss. The tendency of the tape to fly over the head caused by entrained air acting as a bearing, and the presence of debris at the interface between the tape and head which lifts the tape away from the head gap are primary causes of tape-to-head spacing.
A variety of solutions have been advanced in the prior art for attacking the spacing loss problem. Shaping the head contour to effect improvement has been disclosed in U.S. Pat. No. 4,853,814 issued in the name of McClure, where the head has a radius of curvature equal to the natural bending radius of the tape to provide a constant wear characteristic, and has steep shoulders for skiving the tape surface in order to remove entrained air and debris adhering to the tape. In U.S. Pat. No. 4,875,129 issued in the names of Favrou et al, a constant wear profile head assembly is disclosed having slots in the head structure to perform the skiving of the tape surface.
In order to ensure optimum contact between the magnetic tape and the head at the transducing gap, it is necessary to provide a tape path whose geometry is such that tension applied to the tape has a component that forces the tape surface against the contour of the head at the gap line. Tape being abrasive and head materials being refractory, this force component causes undesired mutual abrasion of the tape and head as well as the desired skiving of the air bearing and debris at the steep shoulders or slots of a head. Head wear at the gap is particularly undesirable as the head becomes inoperable if it is worn through at the gap. Thus, in the prior art, the combination of skiving surfaces at the head and tension in the tape has detrimental abrasive side effects that must be accepted in guaranteeing intimate tape head contact for both uni-directional and bi-directional recording and playback operations.